The present invention relates to a differential limiting torque control system for controlling a differential (or slip) limiting torque (or force) of a limited slip differential.
Japanese patent provisional publication No. 62-103227 (Application No. 60-244677) discloses one conventional example. This conventional device employs a progressive characteristic of the differential limiting torque with respect to a left and right drive wheel speed difference in order to provide reliable control performance even in an abrupt one wheel slip state.
Japanese patent provisional publication No. 61-102320 (Application No. 59-223486) discloses another conventional example. In order to prevent an inside wheel from being stuck during a turn, this control system is arranged to decrease the differential limiting torque if the steering amount is large, the accelerator opening degree is great, and the friction coefficient of a road surface is high under the condition that the vehicle speed is equal to or lower than a predetermined speed value.
However, the former system is arranged to increase the differential limiting torque in proportion to the left and right wheel speed difference, and the latter system is arranged to increase the differential limiting torque in proportion to the accelerator opening degree. These conventional system use only the left and right drive wheel speed difference or the accelerator opening degree as a control parameter even when the yaw rate of the vehicle becomes so high as to incur spin of the vehicle. Therefore, these systems hold the differential limiting torque high, so that the possibility of vehicle spin is high.